The present invention relates generally to the field of feedback controllers. The present invention relates more specifically to systems and methods for determining an appropriate sampling rate for a feedback controller.
Feedback controllers are used to control a wide variety of systems and processes. Typically, a feedback controller receives a measured value of a controlled variable (e.g., a feedback signal) and adjusts an input provided to a control device based on the measured value. The object of feedback controllers is to adjust the input provided to the device in a way that maintains a controlled variable at a desired setpoint.
Many feedback controllers respond to a feedback signal based on one or more control parameters. One control parameter frequently used in feedback control processes is a proportional gain (i.e., the proportional term, the gain, etc.). Feedback controllers typically apply the proportional gain as a multiplier to an error signal (e.g., a difference between a setpoint and a feedback signal) in determining an input to provide to the controlled system or process. In addition to the proportional gain, feedback controllers can use other control parameters such as an integral term (e.g., in a proportional-integral (PI) controller) and/or a derivative term (e.g., in a proportional-integral-derivative (PID) controller, etc.).
For dynamic systems in which conditions outside of the control loop affect the controlled variable or where an aspect of the control loop is variably imperfect, the optimal control parameters may also be dynamic. Accordingly, some feedback controllers automatically adjust the control parameters (e.g., the controller is “tuned”) based on observed behavior of the system. Some feedback controllers include adaptive tuning algorithms that automatically adjust the control parameters during normal operation. Such adaptive tuning algorithms can provide for improved performance relative to other tuning strategies.
The rate at which measurements are collected from the controlled system or process (e.g., the sampling rate) can affect the operation of an adaptive tuning algorithm. If the sampling rate is too fast, the feedback controller may tune improperly and the proportional gain may be too small. If the sampling rate is too slow, the performance of the feedback controller may suffer. It is often challenging to determine an appropriate sampling rate for a feedback control system.